CVE-2017-5494 in b2evolution
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in the file types table in b2evolution through 6.8.3 allow remote authenticated users to inject arbitrary web script or HTML via a .swf file in a (1) comment frame or (2) avatar frame.
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Analysis
by VulDB Data Team • 05/13/2026
The vulnerability identified as CVE-2017-5494 represents a critical cross-site scripting flaw within the b2evolution content management system version 6.8.3 and earlier. This vulnerability specifically targets the file types table functionality, which processes various file uploads including flash files with .swf extension. The flaw arises from insufficient input validation and sanitization mechanisms that fail to properly handle malicious content embedded within these file types, creating a pathway for persistent XSS attacks.
The technical implementation of this vulnerability stems from the system's inadequate handling of file metadata and content validation during the upload process. When authenticated users upload .swf files, the system stores these files within comment or avatar frames without sufficient sanitization of embedded script content. This allows attackers to craft malicious flash files that contain embedded javascript or html code, which executes in the context of other users' browsers when the file is rendered. The vulnerability operates through the principle of stored cross-site scripting where malicious payloads are permanently stored on the server and executed whenever legitimate users view the affected content.
The operational impact of CVE-2017-5494 extends beyond simple script injection, potentially enabling attackers to hijack user sessions, steal sensitive information, or perform unauthorized actions on behalf of victims. The authenticated nature of the vulnerability means that attackers need valid user credentials, but once compromised, they can leverage this weakness to maintain persistent access to the system. The attack vector specifically targets user-generated content areas where .swf files are processed, making it particularly dangerous in environments where user uploads are common and trusted. This vulnerability aligns with CWE-79, which defines cross-site scripting as a common web application security flaw, and maps to ATT&CK technique T1059.007 for script execution through web applications.
Mitigation strategies for this vulnerability involve multiple layers of defensive measures including immediate patching of the b2evolution system to version 6.9.0 or later where the issue has been resolved. Additionally, administrators should implement strict file type validation and sanitization processes that prevent .swf file uploads or thoroughly sanitize embedded content within these files. Input validation should be enhanced to strip or encode potentially dangerous characters, and the system should employ Content Security Policy headers to limit script execution. Regular security audits of file upload mechanisms, implementation of web application firewalls, and user education regarding the risks of uploading untrusted content form essential components of a comprehensive defense strategy. Organizations should also consider implementing automated scanning tools to detect and prevent malicious file uploads before they can be processed by the system.